Metals and Non-metals — Detailed Notes

Chapter 3 | NCERT Class 10 Science

3.1 Physical Properties

Metals

Lustre when clean; malleable (beaten into sheets — Au, Ag most malleable); ductile (drawn into wires — Au most ductile; ~2 km wire from 1 g gold)
Generally hard (Na soft — cut with knife); sonorous
Good conductors of heat (Ag, Cu best; Pb, Hg poorer) and electricity
Solids at room temperature except mercury (liquid); Ga, Cs melt on palm

Non-metals

Solids or gases except bromine (liquid)
Not malleable/ductile; generally poor conductors — graphite conducts electricity
Exceptions: lustrous iodine; diamond hardest, high m.p.; alkali metals soft/low density

Physical properties alone are not enough for classification — use chemical properties too.

Most metal oxides → basic; most non-metal oxides → acidic (or neutral).

3.2 Chemical Properties of Metals

3.2.1 Metals + air (oxygen)

$Metal + O_{2} \to Metal oxide$

$2 Cu + O_{2} \to 2 CuO; 4 Al + 3 O_{2} \to 2 Al_{2} O_{3}$

Amphoteric oxides (react with acids and bases): Al₂O₃, ZnO.

$Al_{2} O_{3} + 6 HCl \to 2 AlCl_{3} + 3 H_{2} O$

$Al_{2} O_{3} + 2 NaOH \to 2 NaAlO_{2} + H_{2} O$

Na₂O, K₂O dissolve in water → alkalis. Na, K catch fire in air → stored in kerosene. Mg, Al, Zn, Pb form protective oxide films. Anodising thickens Al oxide coat.

Reactivity with O₂ varies: Na most vigorous among common samples; Ag, Au do not react even at high T.

3.2.2 Metals + water

$Metal + H_{2} O \to metal oxide + H_{2}; oxide + H_{2} O \to hydroxide (if soluble)$

Metal	Behaviour
K, Na	Violent with cold water; H₂ may catch fire
Ca	Less violent with cold water; floats (H₂ bubbles)
Mg	Hot water → Mg(OH)₂ + H₂; floats
Al, Fe, Zn	Steam → oxide + H₂
Sn, Pb, Cu, Ag, Au	No reaction with water (Sn/Pb very slow or negligible under NCERT conditions)

$2 Na + 2 H_{2} O \to 2 NaOH + H_{2} + heat$

$3 Fe (s) + 4 H_{2} O (g) \to Fe_{3} O_{4} (s) + 4 H_{2} (g)$

3.2.3 Metals + acids

$Metal + dilute acid \to salt + H_{2}$

Generally no H₂ with HNO₃ (strong oxidising agent) except very dilute HNO₃ with Mg, Mn.

Aqua regia (conc. HCl : conc. HNO₃ = 3:1) dissolves Au, Pt.

Reactivity with dilute HCl (demo): Mg > Al > Zn > Fe; Cu no reaction.

3.2.4 Displacement from salt solutions

More reactive metal displaces less reactive metal:

$Fe + CuSO_{4} \to FeSO_{4} + Cu$

3.2.5 Activity series (decreasing reactivity)

K, Na, Ca, Mg, Al, Zn, Fe, Sn, Pb, [H], Cu, Hg, Ag, Au

(Do not omit Sn — tin sits between iron and lead.)

Mnemonic: “King Nathan Can Make All Zebras In The Park Look Happy — Copper Has Silver Gold”
→ K Na Ca Mg Al Zn Fe Sn Pb [H] Cu Hg Ag Au

Above H → can displace H₂ from dilute acids
Higher metal displaces lower from salt solution

3.3 How Metals and Non-metals React — Ionic Compounds

Ionic bond — Formation of ionic bond (NaCl idea)

Metals lose electrons → cations; non-metals gain → anions. Transfer forms ionic / electrovalent compounds (e.g. NaCl, MgCl₂). NaCl exists as ion aggregates, not discrete molecules.

Properties of ionic compounds

Solid, hard, brittle
High melting/boiling points (strong ionic attraction)
Generally soluble in water; insoluble in kerosene/petrol
Conduct electricity in molten state or aqueous solution (ions free to move); not in solid state

3.4 Occurrence and Extraction of Metals

Mineral: natural element/compound in earth’s crust
Ore: mineral from which metal can be profitably extracted
Gangue: impurities (soil, sand)
Metallurgy: extraction from ores + refining

Native (free): Au, Ag, Pt, Cu (also combined). Highly reactive metals never free.

By reactivity (summary)

Position	Method
Low (Hg, Cu…)	Heating alone / roasting sulphides
Middle (Zn, Fe, Sn, Pb…)	Roast or calcine → oxide → reduce with C (or Al displacement / thermit)
High (K, Na, Ca, Mg, Al)	Electrolytic reduction of molten compounds

Roasting: sulphide + excess air → oxide
Calcination: carbonate + limited air → oxide

$2 ZnS + 3 O_{2} Heat 2 ZnO + 2 SO_{2}$

$ZnCO_{3} Heat ZnO + CO_{2}; ZnO + C \to Zn + CO$

Thermit: $Fe_{2} O_{3} + 2 Al \to 2 Fe + Al_{2} O_{3} + Heat$ (join railway tracks).

Electrolysis example (NaCl molten): cathode $Na^{+} + e^{-} \to Na$ ; anode $2 Cl^{-} \to Cl_{2} + 2 e^{-}$ .

Electrolytic refining

Impure metal = anode; pure strip = cathode; metal salt solution = electrolyte. Pure metal deposits on cathode; insoluble impurities = anode mud.

Better Method / Strategy
For extraction questions: locate metal on series → choose heating / carbon reduction / electrolysis.

3.5 Corrosion

Ag → black Ag₂S
Cu → green basic copper carbonate (moist CO₂)
Fe → brown flaky rust (needs both air and water)

Prevention: painting, oiling, greasing, galvanising (Zn coat), chrome plating, anodising, alloying.

Galvanisation: even if Zn coat broken, iron still protected (Zn more reactive).

Alloy: homogeneous mixture of metals, or metal + non-metal.
Examples: brass (Cu+Zn), bronze (Cu+Sn), solder (Pb+Sn, low m.p.), steel (Fe+C), stainless steel (Fe+Ni+Cr), 22 carat gold, amalgam (Hg alloy). Alloys often lower conductivity/melting point than pure metals.

Exam-Oriented Analysis

Aspect	Detail
Weight	Major chemistry chapter
Question types	Series predictions; amphoteric; extraction; refining; rust; alloys; exceptions
Common mistakes	Saying solid ionic salts conduct; wrong extraction for Al/Na; rust with only air or only water
Scoring tips	State series order; write both half-ideas for ionic conduction

Non-metals (chemical summary from NCERT “What you have learnt”)

Gain electrons → anions
Oxides acidic or neutral
Do not displace H₂ from dilute acids; form hydrides with H₂